Postage stamps honoring Mercury astronaut Alan Shepard, America’s first man in space, and NASA’s MESSENGER probe, the first spacecraft to orbit Mercury, will be presented on May 4th at a public event taking place at the Aviation Heritage Park in Dayton, Ohio.
Alan Shepard poses in his pressure suit before his historic flight on May 5, 1961. Credit: NASA.
The first stamp salutes NASA’s Project Mercury, America’s first manned spaceflight program, and astronaut Alan B. Shepard, Jr.’s historic sub-orbital flight on May 5, 1961 aboard the spacecraft Freedom 7.
The other stamp highlights NASA’s MESSENGER spacecraft currently exploring the planet Mercury. It successfully established orbit around the planet on March 18, 2011, the first spacecraft ever to do so.
These two historic missions frame a remarkable fifty-year period in which the U.S. has advanced space exploration through more than 1,500 manned and unmanned flights.
Both stamps were designed by professional artist Donato Giancola of Brooklyn, NY, who based the stamp designs on NASA photos and images.
Both stamps will be issued as “Forever Stamps” for use in mailing a one-ounce letter. Regardless of when the stamps are purchased and no matter how postage prices may change, these stamps will always be equal to the current First-Class Mail one-ounce price.
NASA's Mercury-Redstone 3 rocket, with Alan Shepard inside the Freedom 7 capsule, launches from Cape Canaveral on May 5, 1961. Credit: NASA.
Stamps are now available online at the US Postal Service store here.
An unnamed crater on Mercury taken by MESSENGER's Narrow Angle Camera. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Buried treasure on Mercury? If so, I’d look here first. This image shows a currently unnamed crater with an “X” emblazoned on it. The perpendicular lines that cross the crater are secondary crater chains caused by ejecta from two primary impacts outside of the field of view, according to MESSENGER scientists. MESSENGER has been in orbit of Mercury since mid-March of this year, and its Mercury Dual Imaging System (MDIS) pivot and Narrow Angle Camera (NAC) spotted this unusual landform. MESSENGER will be mapping more than 90% of Mercury’s surface as part of a high-resolution surface morphology base map that will be created with MDIS.
Set your alarm clocks for an early treat about a half an hour before sunrise on Thursday April 28 through Sunday, May 1, 2011, as there will be a planetary delight in store! Go out and with either a pair of binoculars, a small telescope, or just use your naked eyes and find an unobscured view of the Eastern horizon to see a conjunction (objects near each other in the sky) of the planets Jupiter, Mars, Venus and Mercury, below and to the left of the thin crescent moon.
Bright Venus will be easy to spot first, then Mercury followed by Jupiter. The real challenge is to find Mars which will be very close to Jupiter. See the above diagram for help on where each object is located.
If you are unlucky on the first morning, try again the following day for a chance to see this rare planetary occurrence.
While observing this close to the Sun take care and never look at the sun directly with your eyes and never through an optical instrument, as this will permanently damage your eyesight or blind you!
Only special purpose made solar telescopes and filters are safe for viewing the sun.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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The MESSENGER spacecraft is still happily orbiting Mercury since its orbit insertion in mid-March, and here are some of the latest images sent back from the first rock from the Sun. In this image, the central peaks inside a large crater named Asvaghosa show up as exceptionally bright. The MESSENGER team believes that their high reflectance appears to have been enhanced by the crater rays that cross the area, which originates from another crater. Asvaghosa is 90 km (56 mi.) in diameter, and was targeted for special, high-resolution observations, where MESSENGER’s cameras zero-in for the closest looks possible. While it is not possible to cover all of Mercury’s surface at this high of a resolution during the spacecraft’s one-year mission, several areas of high scientific interest are generally imaged in this mode each week.
See more below!
Oblique view of Bek crater on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
What a unique, swirling crater — and this high-resolution view of Bek crater (32 km (20 miles) in diameter) has me trying to imagine scaling the cliffs seen in this incredible vista. The MESSENGER team says that the sharp crater rim is in contrast to its subdued surroundings, where crater ejecta scoured the surface and left behind many secondary craters.
'Weird terrain' inside the crater Petrarch on Mercury. Credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
When scientists from the Mariner 10 team first saw this region around Petrarch crater, they called it “weird terrain.” The rugged terrain has an unusual “hilly and lineated” that may have been modified by converging seismic waves and/or ejecta from the formation of the Caloris basin, which is located on the opposite side of the planet. Now, MESSENGER viewed this area under differing lighting conditions than those seen during MESSENGER’s second flyby and Mariner 10’s first pass. The large, smooth area in the upper left is the floor of Petrarch.
If you fell victim to an April Fool’s prank, then consider that life can play some of the most ironic jokes of all. On April 1, 2011 the Mercury MESSENGER was taking some of its first images from Mercury’s orbit when it accidentally captured the totally unexpected… the ancient Mariner 10.
According to the NASA Press Release, the first reaction of some on the MESSENGER team was that the feature to the left of Mercury’s limb must be an imaging artifact. “It’s the effect of solar neutrinos on the WAC’s CCD,” pronounced Project Scientist Mack Knott. The imaging team was skeptical of this explanation, however, and all Knott could add was “I could explain it to you, but you’d have to understand Feynman diagrams.”
The imaging team brought the anomalous image to the attention of Mission Systems Engineer E. Finn Again, who immediately called an emergency gathering of the Collision Avoidance Review Board. Fortunately, the unusual object in the image did not appear to be in the immediate path of MESSENGER’s next few orbits, but the fact that earlier and subsequent images of the same scene did not include the object prevented a determination of its trajectory.
One of MESSENGER’s Science Team members, Prof. S. T. Rom, recognized the object immediately as Mariner 10, the only spacecraft before MESSENGER to have visited Mercury. Launched in 1973, Mariner 10 flew by Mercury three times in 1974 and 1975 before communication with the probe was lost. Prof. Rom is the only member of the MESSENGER team to have served on the science team of Mariner 10 as well.
The Science Operations Center was filled at the time with MESSENGER team members, and everyone proceeded at once to theorize on why Mariner 10 might appear in an MDIS image of Mercury. Mission design lead Mick Adams quickly calculated that Mariner 10 should not be encountering Mercury on this date. “Mariner 10 and Mercury were in a resonant state that brought the spacecraft by the planet once every two Mercury years. By my calculation, this appearance is 23 days early.”
Guidance and control lead E. C. Shaughn offered that the effect of solar radiation should have substantially altered Mariner 10’s orbit over the past 36 years as a result of solar sailing. Propulsion lead Brecht Engel added that some residual propellant after Mariner 10’s last propulsive maneuver may have outgassed, and that multiple outgassing events may also have contributed to trajectory changes.
MESSENGER’s navigation team members, all of whom are named Williams, plugged these suggestions into their codes. Minutes later they were able to announce to all assembled that Mariner 10 appeared to be in a new resonant state, one synchronous with Earth’s period. The ancient spacecraft is locked into an orbit that swings it by Mercury once every Earth year, on April 1st.
There’s no joke like a cosmic one!
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. And also thanks to H. Levenson!
Smooth plains on Mercury's northern hemisphere. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Sharing just a few of the 1,500 images the MESSENGER spacecraft has now taken from its orbital vantage point, mission scientists are understandably excited – if not overwhelmed – by the data being returned from Mercury. “The instruments are all working marvelously and returning data,” said MESSENGER Principal Investigator Sean Solomon. “The imaging system was turned on earlier this week and over 1,500 images will be acquired over a 3 day period. That is more images than were taken during any of the flybys by the spacecraft.”
Solomon said some of the first images were taken precisely 37 years after the first spacecraft flew by Mercury, Mariner 10 in 1974. “We have now closed the loop begun by Mariner 10, culminating with the first insertion of a spacecraft in orbit.”
2,430 days ago the MESSENGER lifted off from Earth, and after three flybys and a nearly 5 billion mile journey, the spacecraft’s thrusters fired for 15 minutes back on March 17, enabling the spacecraft to ease into orbit.
While already finding intriguing features – many which pose more questions than answers, Solomon reminded reporters during a press conference call today that “all the big questions about Mercury are meant to be answered in a year of observations, not just a couple of days, so we’ll look forward to what is yet to come.”
The top image shows an area of Mercury’s north polar region, revealing terrain that had not been previously seen by spacecraft. The long shadows also accentuate the topography of the surface, which includes a number of ridges, but an unusually smooth surface. Solomon said understanding the interiors of the craters in Mercury’s polar regions and any ices they may contain is one of the main science goals of the MESSENGER mission. “Radar images of Mercury that are now 20 years old suggested that water ice could be in the interiors of these craters,” Solomon said. “That is a hypothesis we’ve been aching to test for 20 years, and now we’ll be able to peer into those crater floors.”
This WAC image showing a never-before-imaged area of Mercury’s surface was taken from an altitude of ~450 km (280 miles) above Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This is another region never seen before by spacecraft. “This is probably a plain deposit formed by undulating ridges and a host of secondary craters formed when a large crater was formed out of the field of view,” Solomon said. “We’re seeing that secondary craters (those formed from the ejecta of another crater) are very pervasive across the surface.”
Solomon added that they are seeing secondary craters that are larger than most secondary craters, compared to those on the Moon and other planetary bodies. “They are surprisingly large,” he said. “ A lot of questions raised by images taken so far and have a large menu of questions we’ll be pursuing over the mission.”
Beautiful bright crater on Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The crater near the bottom of this image is a beautiful example of a relatively small, simple, fresh impact feature on Mercury.The bright ejecta and rays are symmetrically distributed around the crater, indicating that the body that struck Mercury to form the crater approached on a path that was not highly inclined from the vertical.
MESSENGER Systems engineer Eric Finnegan told reporters that it takes about 6 minutes for data to be relayed from the spacecraft to Earth, as Mercury (and the spacecraft) is about .71 AU away, the equivalent of about 106 million km (66 million miles). MESSENGER is in an elliptical orbit, and at its closest point in orbit (periapsis) is about 250 km away from Mercury, and at its farthest point (apoapsis) is about 1,500 km away.
Wide Angle Camera color image of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This is one of the first color images from MESSENGER in orbit. Solomon said the Wide Angle Camera is not a typical color camera. It can image in 11 colors, ranging from 430 to 1020 nm wavelength (visible through near-infrared). “We will be taking global images in at least 8 filters to get a sense of the color variation, which shows the variations in composition and depth of surface features exposed by the action of impact cratering from Mercury’s history.”
From Orbit, Looking toward Mercury's Horizon. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Images like this were frequently seen during MESSENGER’s three flybys. But now that the spacecraft is in orbit of Mercury, views of Mercury’s horizon in the images will be much less common. Occasionally, however, in order to obtain images of a certain portion of Mercury’s surface, the horizon will also be visible. But Solomon said MESSENGER’s goal is to get a set of global data for the planet. “An entire global perspective is unfolding and will continue to unfold over next few months,” he said.
Bright rays, consisting of impact ejecta and secondary craters, spread across this NAC image and radiate from Debussy crater, located at the top. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
This is a closeup Debussy Crater, which was the object of the first image released by MESSENGER yesterday. When asked about the age of this crater, Solomon said it is difficult to give a hard age to craters on Mercury due to not having samples in hand, like to do for the Moon. “On the moon ones that are bright like this, such as Copernicus, were formed in the last 20% in the history of the planet. We see only a handful of bright craters like Debussy on Mercury.”
“When you see a crater that is so bright,” Solomon continued, “ it is because it has not gone through the process of space weathering, completely. Brightness of craters identifies them as being younger than the rest of the terrain, as it hasn’t had the time to have their characteristics altered by age, as those of us with gray hair know.”
Solomon said Debussy was likely created by in impact of an object 5-10 km across.
“Orbits of most asteroids and comets that encounter Mercury are traveling at a much higher speed than planetary bodies farther out from the Sun, and that shows in the amount of melt shown in the surface of Mercury. But still a lot we have to learn about that. Craters at different states of decay and degradation will tell us more about this.”
Altimetric profiles obtained on 29 March during the first two successive MESSENGER orbits on which the Mercury Laser Altimeter (MLA) instrument was operating. Credit: NASA/Goddard Space Flight Center/MIT/Johns Hopkins University Applied Physics Laboratory
This graph shows the first two topographic profiles that were obtained from orbit by the Mercury Laser Altimeter (MLA). “This shows rich detail that we’ve just begun to analyze,” Solomon said, “showing exquisite detail, and we’ll be able to see the topography at both scales of individual geological features and global regions.”
This plot depicts measurements of the strength of Mercury's internal magnetic field measured on 10 successive MESSENGER orbits. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
One big question is about Mercury’s magnetic field. This illustrates the measurements made from 10 orbits of MESSENGER’s magnetometer. In a span of 5 days, messenger has tripled the mount of observations of the planet’s magnetic field, so Solomon said the science team is quickly ramping up a much larger data set to see the geometry of Mercury’s magnetic field, which might help explain why the solar system’s smallest planet still has a magnetic field when the larger planets Mars and Venus do not.
Moreover, because of MESSENGER’s orbit, the maximum magnitude of the measured field was greater than that seen during any of the spacecraft flybys. Solomon said these observations are improving our understanding of Mercury’s magnetic field and how its magnetosphere can change over timescales of minutes, how the solar activity and interaction between the Sun and the planet affect the magnetic field.
“As the Sun’s activity ramps up, it is an exciting time to be at Mercury and have a ringside perspective,” Solomon said.
MESSENGER's first image from Mercury orbit, with the bright Debussy crater visible at upper right. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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Here it is, the first image taken by the MESSENGER spacecraft since entering orbit around Mercury on March 17, and it includes portions of the planet not yet previously seen by spacecraft. The image was taken on today, March 29, 2011 at 5:20 am EDT by the Mercury Dual Imaging System as the spacecraft sailed high above Mercury’s south pole. The dominant rayed crater in the upper portion of the image is Debussy, and the smaller crater Matabei with unusual dark rays is visible to the west of Debussy. The bottom portion of this image near Mercury’s south pole is new territory, with MESSENGER being the first spacecraft to image this region of Mercury.
After capturing its first image, MESSENGER acquired an additional 363 images during six hours before downlinking some of the data to Earth. The MESSENGER team is currently looking over the newly returned data, which are still continuing to come down.
The image was acquired as part of the orbital commissioning phase of the MESSENGER mission. Over the next three days, the spacecraft will acquire 1,185 additional images in support of MDIS commissioning-phase activities. Continuous global mapping of Mercury will begin on April 4.
“The entire MESSENGER team is thrilled that spacecraft and instrument checkout has been proceeding according to plan,” says MESSENGER Principal Investigator Sean Solomon, of the Carnegie Institution of Washington. “The first images from orbit and the first measurements from MESSENGER’s other payload instruments are only the opening trickle of the flood of new information that we can expect over the coming year. The orbital exploration of the Solar System’s innermost planet has begun.”
Several other images will be released tomorrow, March 30, in conjunction with a media teleconference. We’ll get them posted as quickly as possible!
Artist's concept of MESSENGER in orbit around Mercury. Courtesy of NASA
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After more than a dozen laps through the inner solar system, NASA’s MESSENGER spacecraft appears to have moved into orbit around Mercury tonight. Although Mariner in the 1970s and MESSENGER in the past several years have done flybys, MESSENGER is the first spacecraft to orbit the innermost planet in our solar system. NASA is stopping short of saying the spacecraft has achieved its planned orbit, but the clapping and hand-shaking in the control room looked highly optimistic.
“Preliminary results show that the burn went just as expected,” said a jubilant Ken Hibbard, an engineer at John Hopkins University’s Applied Physics Lab (APL), in a live report on NASA TV.
UPDATE, 9:50 p.m. EDT: NASA has abandoned all its cautionary language. MESSENGER is confirmed in orbit!
MESSENGER — which stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging — launched Aug. 3, 2004 from Cape Canaveral. The orbit insertion places the spacecraft into a 12-hour orbit about Mercury with a 200 kilometer (124 mile) minimum altitude. The durable spacecraft is carrying seven science instruments and is fortified against the blistering environs near the sun.
The mission is an effort to study the geologic history, magnetic field, surface composition and other mysteries of the planet. The findings are expected to broaden our understanding of rocky planets, more and more of which are being discovered in other solar systems. One of the most compelling enigmas surrounds Mercury’s magnetic field. At a diameter only slightly larger than that of the moon (about 4,800 kilometers or 2,983 miles), Mercury should have solidified to the core. However, the presence of a magnetic field suggests to some researchers that the planet’s insides could be partially molten.
During its journey toward Mercury, MESSENGER passed the planet several times, filling in the imaging gaps left by Mariner 10. Now, the entire planet with the exception of about five percent has been observed. MESSENGER will focus its cameras on getting the best possible images of the remaining portions, mostly in the polar regions.
The MESSENGER mission is led by NASA, APL and the Carnegie Institution and includes a highly dedicated team of engineers, and many scientists.
“I’ve waited 36 years for this, and I’m about as excited as a person could get right now,” said Robert Strom, a MESSENGER team member from the University of Arizona’s Lunar and Planetary Lab.
Planned footprint for the first image to be acquired from a spacecraft orbiting Mercury, on March 29, including a portion of Mercury's surface not previously seen by spacecraft. Over the subsequent six hours, MESSENGER will acquire 364 images in total before beginning to downlink the data to Earth. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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When MESSENGER streaked into the early morning sky over Cape Canaveral on Aug. 3, 2004, very little was known about Mercury.
That could soon change. This week, MESSENGER — which stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging — will make history when it becomes the first spacecraft to orbit Mercury.
At 8:45 p.m. EDT on Thursday, MESSENGER will execute a 15-minute maneuver that will place it into orbit around Mercury, kicking off a year-long science campaign to understand the innermost planet. The craft will fly around Mercury 730 times in the first year, and may be extended for another year after that.
No spacecraft had approached Mercury since the Mariner 10 space probe performed three fly-by maneuvers over the course of 1974 and 1975, imaging the planet’s surface. However, Mariner 10 sent back photos of only one side of the planet, leaving the other shrouded in mystery.
The MESSENGER mission — led by NASA, the Applied Physics Laboratory at Johns Hopkins University and the Carnegie Institution — is an effort to study the geologic history, magnetic field, surface composition and other mysteries of the planet. The findings are expected to broaden our understanding of rocky planets, more and more of which are being discovered in other solar systems. One of the most compelling enigmas surrounds Mercury’s magnetic field. At a diameter only slightly larger than that of the moon (about 4,800 kilometers or 2,983 miles), Mercury should have solidified to the core. However, the presence of a magnetic field suggests the planet’s insides are partially molten.
During its journey toward Mercury, MESSENGER passed the planet several times, filling in the imaging gaps left by Mariner 10. Now, the entire planet with the exception of about five percent has been observed. MESSENGER will focus its cameras on getting the best possible images of the remaining portions, mostly in the polar regions.
The in-flight preparations for this historic injection maneuver began on Feb. 8, when several heaters on the spacecraft were configured to condition the bi-propellant used during the maneuver. Starting on March 8, antennas from each of the three Deep Space Network (DSN) ground stations began a round-the-clock vigil, allowing flight control engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to monitor MESSENGER on its final approach to Mercury. Also that day, the spacecraft began executing the last cruise command sequence of the mission. The command load executed until today. Now, the command sequence containing the orbit-insertion burn has begun.
APL is hosting a live webcast about the orbit insertion maneuver starting at 7:55 p.m. EDT on Thursday, March 17.
For those of you living near Johns Hopkins, APL and The Planetary Society will co-host a public lecture in APL’s Kossiakoff Center, featuring MESSENGER Project Scientist Ralph L. McNutt, Jr. The lecture will begin at 8 p.m. on Thursday. RSVP online.
Check Universe Today late on Thursday for coverage of the orbit insertion, with input from related talks at the Laboratory for Space Physics (LASP) in Boulder, Colorado. Meanwhile, for more information, check out NASA’s MESSENGER mission website.
[/caption]According to today’s Sky & Telescope press release, two bright planets will shine close together low in the western twilight from Sunday to Wednesday, March 13th to 16th. Anyone can see them with the naked eye. You’ll just need a clear sky and an open view toward the west roughly 40 minutes after sunset, as twilight fades.
Jupiter is the brighter of the two. “Mercury is pretty hard to spot most of the time, so a lot of people have never recognized it in their lives,” says Alan MacRobert, a senior editor of Sky & Telescope magazine. “With Jupiter guiding the way, now’s your chance.”
Jupiter has dominated the evening sky for several months, but now it’s on its way down and out for the season. It’ll be gone in another couple of weeks. Mercury, on the other hand, will climb a little higher in the western twilight by late March. (This refers to viewers in the world’s mid-northern latitudes, including the United States, Canada, southern Europe, and elsewhere between about 30° and 50° north latitude.)
The graphic here shows where to look.
Find a spot with a clear, open view low to the west, and you can watch Mercury passing Jupiter in twilight from March 13 to 16, 2011. Credit: Sky & Telescope magazine
The two planets will appear closest together on Monday and Tuesday, March 14 and 15, when they’ll be only about 2° apart — about the width of your thumb held at arm’s length.
Although the two planets appear close together, they’re not. Jupiter is more than 5 times farther away, at a distance of 550 million miles compared to Mercury’s 102 million miles. That means the light we see from them takes 49 and 9 minutes, respectively, to reach us.
“Don’t miss this chance to do a little astronomy from your backyard, balcony, or rooftop,” says Sky & Telescope associate editor Tony Flanders. “It’s a big universe, and planets await.”
For more skywatching information and astronomy news, visit SkyandTelescope.com or pick up Sky & Telescope, the essential magazine of astronomy since 1941.
